U.S. patent application number 16/478449 was filed with the patent office on 2020-02-06 for a reinforcement system and a method of reinforcing a structure with a tendon.
The applicant listed for this patent is Danmarks Tekniske Universitet. Invention is credited to Jacob Wittrup SCHMIDT.
Application Number | 20200040593 16/478449 |
Document ID | / |
Family ID | 57860681 |
Filed Date | 2020-02-06 |
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United States Patent
Application |
20200040593 |
Kind Code |
A1 |
SCHMIDT; Jacob Wittrup |
February 6, 2020 |
A REINFORCEMENT SYSTEM AND A METHOD OF REINFORCING A STRUCTURE WITH
A TENDON
Abstract
A structure (30), such as a concrete structure, with a
reinforcement system configured for anchoring tendons (40) for
structurally reinforcing the structure (30), said reinforcement
system comprising at least one tendon (40) and at least two
anchorages (10), said least one tendon (40) having a first end and
a second end, said first end of the at least one tendon (40) being
structurally connected to the structure (30) by said at least two
anchorages (10), each of said at least two anchorages (10)
comprising an anchor (15), said anchors (15) being positioned
successively at different positions along the length of said first
end of said at least one tendon. Each of said two or more
anchorages (10) comprises an anchorage block (11), in said
anchorage block (11) is attached to the structure (30), and said
anchorage block (11) accommodates said anchor (15).
Inventors: |
SCHMIDT; Jacob Wittrup;
(Copenhagen, DK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Danmarks Tekniske Universitet |
Kongens Lyngby |
|
DK |
|
|
Family ID: |
57860681 |
Appl. No.: |
16/478449 |
Filed: |
January 17, 2018 |
PCT Filed: |
January 17, 2018 |
PCT NO: |
PCT/EP2018/051106 |
371 Date: |
July 16, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E04C 5/122 20130101;
E04G 23/0218 20130101; E04C 5/127 20130101 |
International
Class: |
E04G 23/02 20060101
E04G023/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 17, 2017 |
EP |
17151810.3 |
Claims
1. A concrete structure with a reinforcement system configured for
anchoring tendons for structurally reinforcing the structure, said
reinforcement system comprising: at least one tendon; and at least
two anchorages, said at least one tendon having a first end and a
second end, said first end of the at least one tendon being
structurally connected to the structure by said at least two
anchorages, each of said at least two anchorages comprising an
anchor, said anchors being positioned successively at different
positions along the length of said first end of said at least one
tendon, each of said two or more anchorages comprising an anchorage
block attached to the structure, and accommodating said anchor.
2. The structure with a reinforcement system according to claim 1,
wherein each of said at least two anchorages comprises a ductility
element, said ductility element having a first end abutting said
anchorage block and a second end abutting said anchor, said
ductility element comprising between its first end and its second
end weakened deformation zones being deformable and thereby
allowing the length of deformation zones on the ductility element
to increase or decrease in an axial direction along the length of
said at least one tendon, when the stress on the ductility element
exceeds a certain level, the ductility element comprising weakened
deformation zones being weaker than the other components of the
reinforcement system, the ductility element being adapted to deform
before the other components of the reinforcement system.
3. The structure with a reinforcement system according to claim 1,
wherein said at least two anchorages comprises a ductility element,
said ductility element is positioned in structural connection,
between said at least one tendon and said anchors, said ductility
element comprising weakened deformation zones being deformable and
thereby allowing the length of deformation zones on the ductility
element to increase or decrease in an axial direction along the
length of said at least one tendon, when the stress on the
ductility element exceeds a certain level, the ductility element
comprises weakened deformation zones being weaker than the other
components of the reinforcement system, the ductility element being
adapted to deform before the other components of the reinforcement
system.
4. The structure with a reinforcement system according to claim 1,
wherein said reinforcement system comprises two or more ductility
elements adapted to deform at different axial loads.
5. The structure with a reinforcement system according to claim 1,
wherein said ductility elements are adapted to deform at loads
being about 30-95%, preferably 70-95% of the stress required for
rupturing of said at least one tendon. cm 6. The structure with a
reinforcement system according to claim 1, wherein the ductility
element is an integrated part of said anchor.
7. The structure with a reinforcement system according to claim 1,
wherein said anchorage block comprises a tightening assembly
adapted to adjust the tensioning of the at least one tendon
relative to the anchorage block.
8. The structure with a reinforcement system according to claim 1,
wherein said anchorage block comprises a recess in the longitudinal
direction of the anchorage block, the recess adapted to accommodate
at least part of the tightening assembly, a part of the at least
one tendon, the ductility element and at least partly the
anchor.
9. The structure with a reinforcement system according to claim 1,
wherein said anchor comprises a barrel having a tapered interior
bore and a compressible wedge adapted to be disposed in said
barrel.
10. The structure with a reinforcement system according to claim 1,
wherein the reinforcement system comprises additionally at least
two or more anchorages adapted for anchoring said second end of the
at least one tendon, said second end of the at least one tendon
structurally connected to the structure by said additionally at
least two anchorages .
11. The structure with a reinforcement system according to claim 1,
wherein the at least one tendon comprises fiber-reinforced polymer
(FRP), including carbon, aramid, or glass fiber reinforced
polymer.
12. A method of reinforcing a structure with at least one tendon
and a reinforcement system, the method comprising: fixing at least
two anchorages to a first end of the at least one tendon, said at
least one tendon being connected to each anchorage successively,
mounting said at least two anchorages to the structure, attaching
at least two anchorage blocks to the structure, fixing two or more
sets of a ductility element followed by an anchor subsequently onto
the first end of the at least one tendon, the two or more ductility
elements and anchors positioned subsequent in an axial direction
along the length of said at least one tendon, and positioning said
two or more sets of ductility elements and anchors into the
recesses of the at least two anchorage blocks.
13. The method of reinforcing a structure with at least one tendon
according to claim 12, the method further comprising: placing a
ductility element at the first end of the at least one tendon in
structural connection to each of said at least two anchorages.
14. The method of reinforcing a structure with at least one tendon
according to claim 12, further comprising the step of: adjusting
the tightening assemblies for adjusting the tensioning of the at
least one tendon relative to the anchorage block.
15. The method of reinforcing a structure with at least one tendon
according to claim 13, further comprising: adjusting the tightening
assemblies for adjusting the tensioning of the at least one tendon
relative to the anchorage block.
Description
[0001] The present invention relates to a reinforcement system
configured for anchoring tendons for structurally reinforcing a
structure such as a concrete structure, said reinforcement system
comprises at least one tendon and at least two anchorages, said
anchorages are adapted to anchoring said at least one tendon to
said structure, said at least one tendon comprises a first end and
a second end.
BACKGROUND OF THE INVENTION
[0002] Reinforcement systems for new structures or existing old
concrete structures, like bridges, buildings, silos, which need
strengthening in order to sustain increasing demand loads is well
known.
[0003] Reinforcement systems comprise reinforcement elements of
steel or fibers, such as FRP cable or rods, e.g. carbon, aramid or
glass fiber reinforced polymer. FRP fibers have been proven to be
an attractive alternative to steel. The FRP alternatives are
typically of the types of carbon (CFRP), glass (GFRP) or aramid
(AFRP) fiber reinforced polymers. The FRP fibers have the
advantages of high strength, light weight and excellent corrosion
resistance compared to conventional reinforcing steel. However
since FRP fibers by themselves can withstand a high level of
tensile stress the behavior of the anchorage of the FRP fibers
becomes very important. Thus, an effective anchorage of the FRP
fibers is necessary for exploit the potential strengthening
capacity of such FRP fibers.
[0004] However, the application of fiber reinforced polymer (FRP)
reinforcement has a problem, as FRP have a low strain capacity and
linear elastic stress-strain behavior up to rupture without
yielding. Also, the weak properties in the transverse direction of
the fibers are a major challenge, since it makes the tendon
difficult to anchor and often a premature failure is the
outcome.
[0005] One of the mayor challenges using fiber reinforced polymers
(FRP) and fiber material in constructions such as concrete is to
get an optimal interaction between such anchoring systems and a
reinforced construction.
[0006] The component, such as an anchor, of an anchoring system has
a crucial importance since it is the contact between the FRP tendon
and the surrounding concrete construction. If the anchor does not
work optimal and provide a stable interaction between the FRP
tendons and the construction the anchoring system fails to work as
desired. The anchorage is typically the weakest link.
[0007] U.S. Pat. No. 6,082,063 discloses an anchorage for a tendon
that includes a sleeve having a smooth tapered interior bore and a
compressible wedge disposed in the sleeve. The compressible wedge
has a smooth exterior tapered surface tapering from a wider end to
a narrower end and one or more interior channels for receiving a
tendon. The taper angle of the compressible wedge is greater than
the taper angle of the bore. Thus, upon insertion of the
compressible wedge into the sleeve, the wider end of the
compressible wedge forms a wedge contact with the sleeve before the
narrower end forms a wedge contact with the sleeve. Hereby is
achieved an appropriate anchorage system for FRP tendons.
[0008] JP 2 884465 B2 discloses an anchorage for a FRP reinforcing
material. The anchorage has a number of anchors attached
successively at different positions along one end of a FRP
reinforcing tendon. The anchors are interconnected by means of
respective springs and thereby form a stack, one end of which abuts
the structure at a point where the tendon is inserted through a
hole in structure.
[0009] WO 2016/079214 A2 discloses a reinforcement system for
anchoring tendons to a structure by means of a single anchorage,
including a ductility element, at either end of the tendon.
[0010] Another drawback by the application of high strength steel
reinforcement or FRP fibers in concrete structures is due to the
lower degree of strain hardening and smaller elongation of the
tensile reinforcement.
[0011] Also ductility of structures is important to ensure large
deformation and give sufficient warning while maintaining an
adequate load capacity before structure failure.
[0012] Concrete is a semi-brittle material. Concrete structures
rely largely on the deformation and yielding of the tensile
reinforcement to satisfy the ductility demand.
[0013] The application of high strength steel reinforcement in
concrete structures has less ductility due to the lower degree of
strain hardening and smaller elongation of the tensile
reinforcement.
[0014] Thus, the ductility of concrete members reinforced with
low-ductile tendons, especially FRP reinforced concrete members,
decreases due to the tensile reinforcement deforms less and hence a
lower deformability and ductility is achieved.
[0015] Due to high strength reinforcements, the anchoring systems
have become relatively large, which is undesirable as different
types of fractures both within the reinforcement system or the
structure to be reinforced can be difficult to control.
[0016] It is desirable to provide an anchoring system that can
transfer high loads between reinforcement elements of steel or
fibers and a structure in a simple and reliable controllable
way.
BRIEF DESCRIPTION OF THE INVENTION
[0017] The object of the present invention is to provide a
reinforcement system that in a controlled way distributes the loads
to the structure as to avoid undesirable peak loads, premature and
brittle ruptures.
[0018] This is achieved by said reinforcement system, wherein each
of said at least two anchorages comprises an anchor, said anchors
are positioned subsequently at different positions along the length
of said first end of said at least one tendon, said first end of
the at least one tendon is structurally connected to the structure
by said at least two anchorages.
[0019] Hereby is achieved that relatively small anchors may be used
together in an anchoring system which provides transfer of high
loads between tendon(s) and a structure in a simple and reliable
controllable way.
[0020] Additionally in many cases, it is desirable to provide an
improved structural ductility of high strength steel or FRP
reinforced concrete members.
[0021] In an embodiment, said at least two anchorages comprises a
ductility element, said ductility element is positioned in
structural connection between said at least one tendon and said
anchors, said ductility element comprising weakened deformation
zones being deformable and thereby allowing the length of
deformation zones on the ductility element to increase or decrease
in an axial direction along the length of said at least one tendon,
when the stress on the ductility element exceeds a certain level,
the ductility element comprises weakened deformation zones being
weaker than the other components of the reinforcement system, the
ductility element being adapted to deform before the other
components of the reinforcement system.
[0022] This results in the ductility element by elongation or
compression increases the ductility in the reinforcement system,
thus providing an improved ductility of reinforced structural
members.
[0023] In an embodiment, the reinforcement system comprises two or
more ductility elements adapted to deform at different axial
loads.
[0024] In an embodiment, the ductility elements are adapted to
deform at loads being about 30-95%, preferably 70-95%, of the
stress required for rupturing of said at least one tendon.
[0025] In an embodiment, the ductility element is an integrated
part of said anchor.
[0026] In an embodiment, each of said two or more anchorages
comprises an anchorage block, said anchorage block adapted to be
attached to the structure, the anchorage block is adapted to
accommodate said anchor.
[0027] In an embodiment, the anchorage block comprises a tightening
assembly, said tightening assembly is adapted to adjust the
tensioning of the at least one tendon relative to the anchorage
block.
[0028] In an embodiment, the anchorage block comprises a recess in
the longitudinal direction of the anchorage block, the recess is
adapted to accommodate at least part of the tightening assembly, a
part of the at least one tendon, the ductility element and at least
partly the anchor.
[0029] In an embodiment, the anchor comprises a barrel having a
tapered interior bore and a compressible wedge adapted to be
disposed in said barrel.
[0030] In an embodiment, the reinforcement system comprises
additionally at least two or more anchorages adapted for anchoring
the second end of the at least one tendon, the second end of the at
least one tendon is structurally connected to the structure by the
additionally at least two anchorages.
[0031] The present invention further relates to a method of
reinforcing a structure with at least one tendon according to the
reinforcement system, wherein the method comprises the steps of;
fixing at least two anchorages to a first end of the at least one
tendon, said at least one tendon is connected to each anchorage
successively, mounting said at least two anchorages to the
structure.
[0032] In an embodiment of the method, the method further comprises
the step of; placing a ductility element at the first end of the at
least one tendon in structural connection to each of said at least
two anchorages.
[0033] In an embodiment, the method further comprises the steps of;
attaching at least two anchorage blocks to the structure, fixing
two or more sets of a ductility element followed by an anchor
subsequently onto the first end of the at least one tendon, the two
or more ductility elements and anchors are positioned subsequent in
an axial direction along the length of said at least one tendon,
positioning said two or more sets of ductility elements and anchors
into the recesses of the at least two anchorage blocks.
[0034] In an embodiment, the method comprises the step of providing
two or more ductility elements adapted to deform at different axial
loads.
[0035] In an embodiment, the method comprises the step of adjusting
the tightening assemblies for adjusting the tensioning of the at
least one tendon relative to the anchorage block.
[0036] The term tendon should be understood as any type of
reinforcement element of steel or fibers, such as FRP cable or
rods, e.g. carbon, aramid or glass fiber reinforced polymer,
although other material also may be used.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] Embodiments of the invention will be described in the
following with reference to the drawings wherein
[0038] FIG. 1 is a side view of a T-shaped structure and a
reinforcement system,
[0039] FIG. 2 is an enlarged side view of the T-shaped structure
and a reinforcement system,
[0040] FIG. 3 is a perspective view of the T-shaped structure and
the reinforcement system as illustrated in FIG. 2,
[0041] FIG. 4 is a top view and a cross sectional view of an
anchorage block,
[0042] FIG. 5 is a bottom view and a side view of the anchorage
block,
[0043] FIG. 6 is two cross sectional views and an end view of the
anchorage block,
[0044] FIG. 7 is a side view of a ductility element,
[0045] FIG. 8 illustrates three embodiments of the ductility
element.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
FIGURES
[0046] The present invention relates to a reinforcement system for
anchoring tendons for structurally reinforcing a structure such as
a concrete structure.
[0047] Generally, the reinforcement system may be cast directly
into a structure, such as a concrete structure, or applied to the
structure afterwards. Furthermore, the reinforcement system may be
used inside a concrete structure as well as on the outside of the
structure, and as the tendons and ductility element may be made of
non-corrosive material, thus it is suitable for being used in more
aggressive environments.
[0048] FIG. 1 illustrates a reinforcement system which comprises
six anchorages 10 attached to a structure 30. The anchorages 10
anchor a tendon 40 to the structure 30.
[0049] Three anchorages 10 are positioned at the first extremity of
the structure 30. The three anchorages are positioned successively
at different positions in an axial direction along the length of a
first end of the tendon 40.
[0050] Another three anchorages 10 are positioned at the second
extremity of the structure 30, and likewise these three anchorages
are positioned successively in an axial direction along the length
of a second end of the tendon 40. Generally, any suitable number of
anchorages may be positioned successively at different positions in
the axial direction along the length of either one of the first or
the second end of the tendon 40.
[0051] The anchorages are adapted to fasten the tendon to a
structure 30.
[0052] FIG. 2 illustrates an enlarged view of the first end of the
tendon 40 and one extremity of the structure 30. The reinforcement
system is attached to the T-shaped structure. Three anchorages 10
attach the tendon 40 to the T-shaped structure 30. The three
anchorages are positioned subsequent along the length of a first
end of the tendon 40. An anchorage 10 comprises an anchorage block
11 and an anchor 15. The anchor comprises a barrel 18 having a
tapered interior bore and a compressible wedge 19. Other types of
anchors may be used.
[0053] This is also illustrated in FIG. 3 in a perspective
view.
[0054] As seen in the figures, and according to the present
invention in general, the respective anchors 15 are individually
connected to the structure by means of respective anchorages 10
attached to the structure successively at different positions along
the respective end of the tendon 40, and at least one end of the
tendon 40 is fixed independently at different positions to the
structure. Each anchorage 10 is individually connected directly to
the structure by means of a respective separate anchorage block 11
which is directly mounted on or in the structure, for instance by
being moulded into the structure or by being mounted by means of
screws or in any other suitable way known to the skilled person. By
means of this arrangement, the load of the tendon 40 is distributed
over the respective anchorages 10 at the at least one end of the
tendon 40. In prior art structures, on the other hand, the load of
a tendon is transferred to the structure by means of only one
anchorage at an end of the tendon. However, the connection of the
anchor to the tendon is typically the weakest point of a
reinforcing structure, due to the wedge of the anchor pressing on
the tendon. Therefore, according to the present invention, by
distributing the load of the tendon 40 over the respective
anchorages 10, each anchor may take up only a part of the total
load, and thereby these anchors do not constitute the weakest
points of a reinforcing structure. Furthermore, if the structure to
be reinforced has weakened areas, such as for instance a cut-out or
a hole in a concrete structure, the load from an end of a tendon
may be distributed accordingly over the structure, for instance by
arranging more anchors in areas without weakened areas and fewer
anchors in the weakened areas, or for instance by arranging anchors
in the weakened areas with associated ductility elements having
relatively more weakened deformation zones (63) and by arranging
anchors in the not weakened areas with associated ductility
elements having relatively less weakened deformation zones
(63).
[0055] Each anchorage 10 illustrated in FIG. 3 comprises an
anchorage block 11, a ductility element 12 and an anchor 15. The
anchors comprise a barrel 18 having a tapered interior bore and a
compressible wedge 19 adapted to be disposed in said barrel 18,
thus the anchors are adapted to affix the tendon 40.
[0056] An anchorage 10 in more details is illustrated in FIG.
4.
[0057] The anchorage 10 comprises an anchorage block 11, a
ductility element 12 and an anchor 15. The anchor 15 comprises a
barrel 18 having a tapered interior bore and a compressible wedge
19. The dimensions are given in millimeter.
[0058] The anchorage block 11 comprises a recess 13 and a
subsequent narrower recess 14. The recesses 13,14 are positioned in
continuation in the longitudinal direction of the anchorage block.
The recess 13 is adapted to accommodate the anchor, and the recess
14 is adapted to accommodate the tendon 40.
[0059] The anchorage block 11 comprises two parallel positioned
flanges 16 extending in the longitudinal direction of the anchorage
block 11. The flanges 16 are positioned opposite each other on each
side of the recess 13. The flanges comprise mounting means 17. The
mounting means 17 are adapted to be attached to the structure
30.
[0060] The anchorage block 11 comprises a tightening assembly 25.
The tightening assembly 25 comprises an elongated frame shaped
structure 20. The elongated frame shaped structure 20 is adapted to
abut the inner surfaces of the recess 13 and accommodate the anchor
15 and the ductility element 12 within the elongated frame shaped
structure 20.
[0061] The narrow inner contact face 21 of the elongated frame
shaped structure 20 abuts the ductility element 12, and the
ductility element 12 abuts the barrel 18 of the anchor 15.
[0062] The reinforcement system comprises a ductility element 12,
which is positioned in structural connection, between said tendon
40 and said anchor 15, said ductility element 12 comprises weakened
deformation zones 63 being deformable in axial direction along the
length of said tendon. The deformation zones are weakened in
relation to the other part of the ductility element. When comparing
FIGS. 1 and 2 with FIG. 3, it is understood that although the
ductility element 12 is positioned between at least the main part
of said tendon 40 and said anchor 15 comprising a barrel 18 having
a tapered interior bore and a compressible wedge 19, said ductility
element 12 has a first end abutting said anchorage block 11 and a
second end abutting said anchor 15. Said ductility element
comprises between its first end and its second end said weakened
deformation zones 63 being deformable.
[0063] The recess 13 is adapted to accommodate the elongated framed
shaped structure 20, which encircles a part of the tendon 40, the
ductility element 12 and at least part of the anchor 15, and the
recess 14 is adapted to accommodate a part of the tendon 40.
[0064] A ductility element 12 is positioned abutting the anchor 15
within the recess 13.
[0065] The tightening assembly 25 comprises adjustment unit 24,
attachment parts 23 and a sleeve 22. The tightening assembly 25 is
adapted to move the ductility element 12 and the anchor 15 relative
to the anchorage block 11 to provide tension to the tendon 40 in
the longitudinal direction. The tightening assembly 25 is adapted
to adjust the tensioning of the tendon 40 relative to the anchorage
block (11).
[0066] The adjustment unit 24 may comprise screw thread adapted to
adjust the reinforcement system. When the adjustment unit 24 is
activated the inner contact face 21 of the elongated frame shaped
structure 20 abuts the ductility element 12, and the ductility
element 12 and the anchor 15 is moved coaxially along the tendon
40.
[0067] The method of reinforcing a structure 30 with at least one
tendon 40 according to the reinforcement system comprises the steps
of; attaching at least two anchorage blocks 11 to the structure 30,
fixing two or more sets of a ductility element 12 followed by an
anchor 15 subsequently onto the first end of the at least one
tendon 40, the two or more ductility elements 12 and anchors 15 are
positioned subsequent in an axial direction along the length of
said at least one tendon, positioning said two or more sets of
ductility elements and anchors into the recesses 13 of the at least
two anchorage blocks 11. Furthermore the method comprises the step
of adjusting the tightening assemblies 25 for adjusting the
tensioning of the at least one tendon 40 relative to the anchorage
block 11.
[0068] The anchor 15 is schematically illustrated as a known type
of an anchor comprising a barrel 18 and wedge 19. The barrel has a
tapered interior bore and the compressible wedge being adapted to
be coaxially disposed in the barrel. The tendon 40 extends through
the center of the wedge, which is wedged coaxially inside the
barrel for clamping the tendon 40, and thereby anchoring the tendon
to a structure 30.
[0069] FIG. 5 illustrates the anchorage block 11 in a bottom view
and a side view. The figure shows a part of the sleeve 21
encircling the tendon 40. The anchorage block 11 comprises flange
16, which comprises mounting means 17. The mounting means 17 are
adapted to be attached to the structure 30.
[0070] The dimensions in the figures are given in millimeter. The
length of the shown embodiment of the anchorage block is 360 mm,
the width of the anchorage block is 150 mm, and the height is 32
mm.
[0071] FIG. 6 illustrates an end view of the anchorage block and
two cross sectional views. The views are indicated in FIG. 4 by the
lines marked B, C and D, respectively.
[0072] The first cross sectional view, as indicated in FIG. 4 by
the line marked B, illustrates the anchorage block comprising two
flanges 16.
[0073] The adjustment unit 24 comprises a hexagon outer shape as a
bolt adapted to be turned for adjusting the reinforcement system.
Coaxial the tendon 40 is arranged within the sleeve 22. A
cylindrical cavity 26 between the tendon 40 and the sleeve 22
enables the tendon 40 to slide within the sleeve 22 when the
anchorage is adjusted.
[0074] The second cross sectional view, as indicated in FIG. 4 by
the line marked C, illustrates the anchorage block and the anchor
15. The anchorage block 11 comprises two flanges 16. The anchor
comprises the barrels 18 and the wedge 19. The elongated frame
shaped structure 20 is arranged between the outer surface of the
barrel 18 and the inner surface of the recess 13 on both sides of
the barrel 18. The elongated frame shaped structure 20 comprises a
U-shaped cross section, the elongated frame shaped structure 20
adapted to abut the inner surfaces of the recess 13.
[0075] The third cross sectional view, as indicated in FIG. 4 by
the line marked D, illustrates the anchorage block and the end of
the anchor comprising the barrel 18 and the wedge 19.
[0076] The wedge 19 comprises recesses extending from the outer
surface of the wedge radially towards the tendon 40.
[0077] FIG. 7 illustrates an embodiment of the ductility element
12.
[0078] The ductility element is cylindrical and comprises a first
end and a second end. Two deformable walls 62 are positioned
between the first and second end and encircles a through going
channel 13 which extends centrally internal through the ductility
element. The through going channel 13 is adapted for receiving a
tendon.
[0079] As the two deformable walls 62 have varying thickness, the
ductility element is able to deform upon loads. The weakened
deformable walls 62 are able to deform in radial direction in
respect of the centerline of the ductility element and the
fluctuation of the deformable wall are illustrated by dotted lines
60 in FIG. 7.
[0080] The deformation of the weakened deformable walls is
illustrated in FIG. 7 by dotted lines. During increasing pressure
the ductility element will, when threshold for elastic deformation
is reached, start to deform followed by a deformation resulting in
a collapse.
[0081] The ductility element 12 has a ductile phase in axial load
less than the tensile strength of the tendons, thus making the
ductility element the weakest link in the reinforcement system, and
the ductility element 12 will reach its strength before the other
components of the reinforcement system.
[0082] The ductility element will deform when the stress excides
the threshold of the ductility element, and it thus provides
ductility to the reinforcement system. Thus ductility is achieved
by applying a ductility element to the reinforcement system.
[0083] FIG. 8 illustrates three embodiments of a ductility element
12. The ductility element 12 comprises weakened deformable zones
63.
[0084] The weakened deformation zones may be provided by slits 63a,
holes 63b, such as voids or bubbles, varying thickness of the
deformable walls, as illustrated in FIG. 7, and/or by use of a
material providing a deformable zone.
[0085] The deformation walls 63c may be adapted to deform along the
periphery of the ductility element in tangential direction.
[0086] The weakened deformation zones 63 are weakened in relation
to the other parts of the ductility element 12. The weakened
deformation zones may also be provided by suitable choice of
material.
[0087] The ductility element 12 may be made of metal such as steel
or aluminum, cementitious material, plastics, or elastic material
such as rubber, composite material or in combination thereof.
[0088] The ductility element is configured such that the force
required for deformation of the ductility element in axial load is
less than the force required for deformation of the tendon. Thus,
the ductility element 12 has a ductile phase in axial load less
than the tensile strength of the tendons, thus making the ductility
element the weakest link in the reinforcement system. The ductility
element 12 will reach its strength before the other components of
the reinforcement system. When the stress excides the threshold of
the ductility of the ductility element, the ductility element will
deform and it thus provide ductility to the reinforcement
system.
[0089] As concrete is a semi-brittle material. Concrete structures
rely on the deformation and yielding of the tensile reinforcement
to satisfy the ductility demand.
[0090] By employing a ductility element in combination with tendons
made of high strength steel or fiber lacking of sufficient
ductility an increased ductility is provided by allowing the
ductility element to deform.
[0091] In an embodiment the reinforcement system comprises two or
more ductility elements 12 which are adapted to deform at different
axial loads.
[0092] Generally, the ductility elements 12 are adapted to deform
at loads being about 30-95%, preferably 70-95% of the stress
required to rupture the at least one tendon 40.
* * * * *